This invention is directed to a process for molding containers, and more particularly, to an improved process for molding partitioned containers from a preform and a separately formed inner wall, wherein the inner wall is secured to the preform prior to molding the container.
Partitioned containers and methods for making the same are well known in the art. In most cases, a preform is used to form the partitioned container, which preform has integrally formed therewith the required partitions or walls and the like for forming the partitions of the finished container. That is, typically a complex mold is required to injection mold or otherwise form a preform having integral partitions extending across the cavity thereof. Alternatively, a simple preform may be formed having a hollow cavity and a separately formed partition subsequently secured therein. In these cases, securing the partition to the inside surface of the preform is problematic in that the partition must be caused to maintain its engagement with the inside surface of the preform during subsequent blow molding operations for forming the container. In addition to withstanding expansion during molding and its securement with the inner surface of the preform, the partition must also reliably maintain its engagement with the inner wall of the container after the container is formed. Still another method of forming a partitioned container is to injection mold the entire container of one construction including the partitions. Typically, multiple fairly large and complex injection molds are required for this method.
The prior art includes a plurality of partitioned containers, none of which cure the problems in forming partitioned containers, as set forth above.
U.S. Pat. No. 5,398,828 to Valyi discloses a blow molded plastic container including an internal support and handgrips. The blow molded container includes at least one internal supporting member integral with the inside wall of the body portion to support the same. The body portion defines lobes connected together by depressions which define a handgrip. The depressions are supported by the internal supporting member. The internal supporting member is formed integral with the preform during molding thereof and is then blow molded into the internal member of the container.
U.S. Pat. No. 5,135,823 to Eales discloses a modular multi-compartmented blow molded container. The container includes partition members for forming the compartments therein which initially form portions of a mold for the container. When molding is complete, the partition members form part of the container, with the molded plastic material of the container substantially surrounding the partition members. In another embodiment, the containers are modular, wherein mating engagement members are formed in facing walls of separate container portions that are joined subsequent to molding. The container portions can be made detachable or permanently attached. Accordingly, in this container, the partitions are provided during molding of the container, wherein the partitions are a part of the mold which are adapted to become a part of the container.
U.S. Pat. No. 5,232,108 to Nakamura discloses a preform having an inner partition wall and a process for making a plastic vessel therefrom having an inner partition wall. The preform has an internal partition wall formed to extend across the interior of the barrel portion of the preform and up from the bottom portion thereof. The internal partition wall is injection molded along with the remaining portion of the preform during the formation thereof. The same wall is later blow molded into the partition for the container.
U.S. Pat. No. 4,277,000 to Jaarsma discloses multi-compartmented containers. The multi-compartmented containers include a molded body and a molded cap secured thereto. The body includes a confining wall forming a space, an internal dividing wall forming separate compartments within the space and a base. A fluid seal is formed by the confining wall and the inside surface of the body of the container. The entire container is formed from injection molding, including the formation of the dividing wall.
U.S. Pat. No. 4,065,536 to Lucus discloses a method of making a precisely partitioned bulbous-shape container. The container is formed from a preform having a partition integrally formed therein during the formation of the preform. Accordingly, the partition is integral to the remaining body portion of the preform.
PCT Application GB89/01362 discloses a partitioned plastic container. The container is formed from an injection molded preform, wherein the preform has an integrally formed partition therein which is also formed during the injection molding process. The preform and partition are later blown into the shape of a container having a partition therein.
There exists a need, therefore, for an improved process for forming a partitioned container which process allows for the use of a simple preform and provides a reliable manner for attaching a separately formed partition thereto and to sustain the attachment during formation of the container to be formed thereby and to the container after formation.